1. Field
Embodiments of the invention relate generally to a semiconductor switch.
2. Background Art
Cell phones include a radio frequency circuit section in which a transmit circuit and a receive circuit are selectively connected to a common antenna through a switch circuit for radio frequency signals. The switch element of such a switch circuit for radio frequency signals has conventionally been based on a HEMT (high electron mobility transistor) made of compound semiconductor. Recently, replacement of the HEMT by a MOSFET (metal oxide semiconductor field effect transistor) formed on a silicon substrate has been under consideration in view of requirements for cost reduction and downsizing.
However, the conventional MOSFET formed on a silicon substrate has large parasitic capacitance between the source or drain electrode and the silicon substrate. Another problem is that the radio frequency signal incurs large power loss because silicon is a semiconductor. In this context, a technique is proposed for forming a switch circuit for radio frequency signals on an SOI (silicon on insulator) substrate (see, e.g., JP-T-2005-515657).
However, further improvement is required for inter-terminal isolation and insertion loss. For instance, a switch for switching high-definition digital television signals requires an isolation of 75 dB or more at a frequency of 1 GHz.